In an electricity storage module formed by stacking multiple electricity storage elements, lead terminals of adjacent electricity storage elements are connected through ultrasonic welding in some cases. In such a case, a gap into which a welding jig is inserted needs to be ensured in the electricity storage module, and therefore the number of layers of the electricity storage elements are limited and the overall size increases in some cases.
As a means for solving the above-described problem, there exists a method of joining lead terminals using laser welding. However, for example, if the metal materials constituting the two electrode terminals are different, as in the case of joining a cathode terminal made of aluminum and an anode terminal made of copper, it is difficult to perform joining through laser welding.
In view of this, if the metal materials constituting the electrode terminals to be connected are different, it is conceivable to use, as a busbar, a clad material obtained by pressure welding a first metal material composed of a metal material of the same type as that of the cathode terminal, and a second metal material composed of a metal material of the same type as that of the anode terminal (e.g., see Patent Document 1).